1. Field of the Invention
The present invention relates to a transmission system for vehicle that performs automatic shifting by controlling a clutch actuator and a shift actuator.
2. Description of Related Art
Japanese Patent Application Publication No. 2012-57654 discloses a control unit that controls a shift stage switching of an automatic transmission in accordance with an accelerator opening and a vehicle speed. An accelerator sensor detecting an operation amount of an accelerator pedal and a vehicle speed sensor detecting a rotational speed of an output shaft of the transmission as the vehicle speed are connected to the control unit. Based on the accelerator operation amount and the vehicle speed detected respectively by the sensors, the control unit references a shift map and calculates a target shift stage. The control unit controls air cylinders for a clutch device and a gear shift unit, respectively, so that the target shift stage is attained.
Slipping of a wheel of a vehicle may occur due to a braking operation performed by a driver. In such a case, the rotational speed of the output shaft of the transmission (vehicle wheel speed) decreases suddenly even though the actual vehicle speed is not decreased. When due to this, a lower speed stage is set as the target shift stage and shifting to the target shift stage is performed, engine over-revolution may occur due to torque input from the vehicle wheel when the slipping is resolved. Japanese Patent Application Publication No. 2012-57654 provides a solution to the problem.
That is, the control unit of Japanese Patent Application Publication No. 2012-57654 prohibits downshifting when the vehicle wheel is put in a slipping state due to a braking operation. Over-revolution of the engine due to inappropriate shift stage selection can thereby be avoided.